Scrub washing method, scrub washing device, lens forming die drying method, lens forming die drying device, and plastic lens manufacturing method

ABSTRACT

A self-washing step of rotating elastic polishing members  230 , supplying a liquid L to the elastic polishing members  230 , and, in this condition, pressing pressing units  220  against the elastic polishing members  230  to deform the elastic polishing members  230 , thereby washing the elastic polishing members  230  themselves is added to a scrubbing step of rotating lens molds  1, 2 , rotating the elastic polishing members  230 , pressing the elastic polishing members  230  against the surfaces of the lens molds, and, in this condition, supplying the liquid to the areas between the surfaces of the lens molds  1, 2  and the elastic polishing members  230 , thereby washing the lens molds  1, 2 . In a drying step, hot water is supplied to the lens molds  1, 2  being rotated, and thereafter dry air is supplied thereto. It is possible to securely remove foreign matter and dirt from the surfaces of the lens molds for molding a plastic lens, and to clean the surfaces of the lens molds without leaving water discoloration or stains thereon.

TECHNICAL FIELD

The present invention relates to a technology for washing and drying alens mold used for cast polymerization molding of a plastic lens and toa method of manufacturing a plastic lens by use of a lens mold.

BACKGROUND ART

FIG. 1 shows a flowchart of a conventionally known method for molding aplastic lens by cast polymerization. The plastic lens molding methodincludes the steps of preparing a female mold and a male mold, washingat least the molding surfaces of the molds by use of an abrasive or achemical, thereafter washing the molds with water, drying the molds tothereby clean the molds, assembling the thus cleaned female and malemolds to form a mold assembly by a tape mold process or the like,injecting a curable composition into the mold assembly, polymerizing andcuring the curable composition, and then demolding the cured product.

FIG. 2 illustrate schematically the tape mold process. As shown in FIG.2(a), a glass-made lens mold (female mold) 1 for molding a convexsurface and a glass-made mold (male mold) 2 for molding a concavesurface are prepared, then, as shown in FIG. 2(b), the convex surfacemolding surface 11 of the female mold 1 and the concave surface moldingsurface 21 of the male mold 2 are opposed to each other, and a pressuresensitive adhesive tape 3 is wound around the circumferential surfacesof the lens molds 1, 2 to seal the gap therebetween, to construct a lensmold assembly 5.

FIG. 3 illustrates an example of a curable composition injection step. Acurable composition 6 is injected into the gap (cavity) 4 between themolds of the constructed lens mold assembly 5 to fill up the cavity 4with the curable composition 6, and then an injection port formed in thepressure sensitive adhesive tape 3 is sealed off. Thereafter, thecurable composition 6 is cured by energy such as heat, UV rays, etc.,whereby a plastic lens can be obtained.

If dirt or foreign matter is present on the lens molds 1, 2, the dirt orforeign matter would be transferred onto the plastic lens obtained, todirectly exert bad effects on the optical surfaces; therefore, it isnecessary to completely remove the dirt or foreign matter. For thispurpose, a method is adopted in which at least the molding surfaces 11and 21 of the lens molds 1, 2 are subjected to precise washingimmediately before wounding the pressure sensitive adhesive tape 3, andthe lens mold assembly 5 is constructed while maintaining thecleanliness.

As a method for washing the lens molds 1, 2, there is an ultrasonicwashing method using a detergent, as described in an embodiment inJapanese Patent Laid-open No. 2000-102932. A method of washing a mold byuse of a sponge roll is described in an embodiment in Japanese PatentLaid-open No. Hei 5-84755. In this washing method, the mold is scrubbedusing a urethane foam while supplying water. Besides, Japanese PatentLaid-open No. Hei 11-48117 discloses a method of reforming the surfaceof an optical member in which the surface is rubbed with a memberobtained by softening an abrasive-containing resin through wetting.

Among these washing methods, the scrubbing method of washing a lens moldby rubbing it with an elastic polishing member is the best for removingcontaminants from the lens mold. In this case, when an abrasive isintermediately present, it is possible to remove the dirt which wouldotherwise be difficult to remove.

However, the scrubbing methods of washing a lens mold by use of thesponge roll or the elastic polishing member obtained by softening anabrasive-containing resin through wetting have the problem that the dirtor foreign matter may remain on the elastic polishing member after thelens mold is washed. If the elastic polishing member with the dirt orforeign matter deposited thereon is directly used for washing the lensmold, the dirt or foreign matter may be transferred onto the surface ofthe lens mold or the lens mold surface may be marred. The dirt orforeign matter or scratches present on the surface of the lens mold maydirectly exert bad effects on the optical surface of the molded lens,thereby lowering the yield of the lens. Besides, in the methods ofwashing a lens mold by use of the sponge roll or the elastic polishingmember obtained by softening an abrasive-containing resin throughwetting, there is the problem that the elastic polishing member would bedried when washing is at rest for a long time, and, when the driedelastic polishing member is directly used for washing, the moldingsurface of the lens mold would be marred. The flaws in the moldingsurface of the lens mold would eventually be transferred onto the lensproduced, thereby yielding defective products and lowering the yield ofthe lens.

The present invention has been made in consideration of the abovecircumstances. Accordingly, it is a first object of the presentinvention to provide a scrubbing method and a scrubbing apparatus bywhich it is possible to wash a lens mold without leaving dirt on thelens mold and without marring the lens mold.

In addition, after the washing of the lens molds 1, 2, it is necessaryto dry the lens molds 1, 2 having been wetted with water. If suchdefects as water discoloration and stains are present on the surfaces ofthe lens molds 1, 2, the defects would be transferred onto the opticalsurfaces of the lens. Therefore, the drying of the lens molds 1, 2having been wetted with water must be so conducted as not to generatesuch defects.

Conventionally, as a method for drying a lens mold having been wettedwith water, there have been proposed a method in which a lens mold isdried by use of a flon-based, alcohol-based or chlorine-based organicsolvent or the like organic solvent (see, for example, Japanese PatentLaid-open Nos. Hei 5-114594 and Hei 5-185042), a method in which a lensmold is immersed in pure water, is then pulled up from pure water and isdrained and dried (see, for example, Japanese Patent Laid-open Nos. Hei6-230325 and Hei 5-50046), and a method in which an organic solvent isnot used and water is blown off by jetting compressed air (see, forexample, Japanese Utility Model Laid-open No. Hei 5-40795 and JapanesePatent Laid-open No. Hei 5-193123). In addition, there has also beenproposed a method in which an optical component part wetted with wateris warmed up by blowing hot air thereto and is then dried in air (see,for example, Japanese Patent Laid-open Nos. Hei 7-124529 and Hei10-199854). Further, there have been proposed a method in which anoptical component part is placed in a hermetically sealed vessel forvacuum drying (see, for example, Japanese Patent Laid-open No. Hei5-172461) and a method in which an optical component part is drained byvibrating it (see, for example, Japanese Patent Laid-open No. Hei5-127397).

However, the drying method using a flon-based organic solvent exerts ahigh burden on the environments because of the use of the ozone layerdestructive substance. The drying method using an alcohol-based orchlorine-based organic solvent, due to the use of the inflammablesubstance, makes it necessary to use an apparatus with explosion-proofspecifications, which is expensive. The drying method utilizing drainingthrough rotation has the merits that the apparatus may be smaller thanin the immersion system and the lens molds can be treated one by one,but the method has the demerit that water or moisture will easily remainin the surroundings of the optical component part and a long time istaken to achieve drying. The method in which the lens mold is immersedin pure water, is then pulled up from pure water and is drained anddried has the problem that an immersion tank with a large capacity isneeded, leading to a large-scale apparatus, and a jig for holding thelens mold is needed. In the method in which water is blown off byjetting compressed air, water thus blown off may re-adhere to thesurface of the lens mold, causing water discoloration, stains or thelike. In the method in which an optical component part wetted with wateris warmed up by blowing hot air thereto and is then dried in air, thedrying process is long, and it is difficult to control the temperatureof the optical component part, which makes it impossible to maintaingood quality. The method in which an optical component part is placed ina hermetically sealed vessel for vacuum drying and the method in whichan optical component part is vibrated for draining are disadvantageousin that a large-scale apparatus is needed.

The present invention has been made in consideration of the abovecircumstances. Accordingly, it is a second object of the presentinvention to provide a lens mold drying method and a lens mold dryingapparatus by which a lens mold can be dried without using an organicsolvent, without needing any large-scale equipment for vacuum drying orthe like, and while promising good appearance quality free of waterdiscoloration, stains or the like.

Besides, the step of injecting the curable composition 6 into the lensmold assembly 5 shown in FIG. 3 is conducted as follows. First, thepressure sensitive adhesive tape 3 is provided with a prepared hole in apredetermined position thereof, and an injection nozzle 7 is insertedinto the prepared hole portion. In the lens mold assembly 5 for moldinga convex lens, the spacing between the two lens molds 1, 2 at acircumferential portion is small, an injection nozzle 7 very small indiameter at the tip end thereof is used so that it can be inserted intothe small spacing. A pressure is applied to the inside of a pressurevessel 8, whereby the curable composition 6 charged in the pressurevessel 8 is fed under pressure through a piping 9 and a valve 10 intothe injection nozzle 7, and is injected into the cavity 4. Upondetection of that the cavity 4 has been filled with the curablecomposition 6, the valve 10 is closed to finish the injection, and theinjection port is sealed off.

Such an injection method as above has had the following problems. Thevolume of the cavity 4 in the lens mold assembly 5 ranges from about 10ml to about 100 ml. However, the tip end of the injection nozzle 7 isvery small in diameter. In order to enhance production capacity,therefore, it is necessary to heat the curable composition 6 to becharged, thereby lowering the viscosity of the curable composition 6 andincreasing the injection flow rate. In view of this, a heater 11 isdisposed on the wall surfaces of the pressure vessel 8, and a heater 12is wound around the piping 9, whereby the curable composition 6 isheated at the time of being charged into the cavity 4. Where the curablecomposition 6 is heated, however, optical strains may be generated inthe plastic lens obtained by molding, with the result of lowering inyield.

The present invention has been made in consideration of the abovecircumstances. Accordingly, it is a third object of the presentinvention to provide a method of manufacturing a plastic lens by whichit is possible to restrain the generation of optical strains in theplastic lens obtained, and to enhance the yield of the plastic lens,even where a curable composition is heated at the time of being injectedinto a lens mold assembly for cast polymerization of the plastic lens.

DISCLOSURE OF INVENTION

In order to attain the first object mentioned above, according to thepresent invention, there is provided a scrubbing method including: awashing step of rotating a lens mold for molding a plastic lens,pressing an elastic polishing member against a surface of the lens moldwhile rotating the elastic polishing member, and, in this condition,supplying a liquid to the area between the surface of the lens mold andthe elastic polishing member so as thereby to wash the lens mold; and aself-washing step of rotating the elastic polishing member, supplying aliquid to the elastic polishing member, and, in this condition,deforming the elastic polishing member so as thereby to wash the elasticpolishing member.

In the washing step, the lens mold is scrubbed with the elasticpolishing member, and, in the self-washing step, the elastic polishingmember itself used for the scrubbing is washed, whereby dirt or foreignmatter adhering to the elastic polishing member can be washed away. Byperforming the self-washing step, the dirt or foreign matter can beprevented from re-adhering from the elastic polishing member onto thelens mold. In addition, by performing the self-washing step, the elasticpolishing member can be prevented from being dried. Therefore, the lensmold can be washed without leaving the dirt or foreign matter on thelens mold and without marring the lens mold.

As the liquid used in the washing step and the self-washing step, aslurry containing an abrasive dispersed in water may be used. In thiscase, in the washing step, the slurry containing an abrasive dispersedin water is supplied to the area between the surface of the lens moldand the elastic polishing member, and the surface of the lens mold ispolished through the abrasive, whereby dirt can be removed effectively.In the self-washing step, the slurry is supplied to the elasticpolishing member, whereby the elastic polishing member itself can bewashed effectively.

As the liquid used in the washing step and the self-washing step, watermay be used. In this case, in the washing step, the surface of the lensmold can be cleaned by scrubbing the surface with water. In theself-washing step, the elastic polishing member is washed with water,whereby dirt or foreign matter having been deposited on the elasticpolishing member itself can be removed.

In the self-washing step, a rod-like member and the elastic polishingmember may be pressed against each other, whereby the elastic polishingmember can be deformed largely, so that the elastic polishing member canbe self-washed effectively.

With the washing step and the self-washing step conducted alternately,the self-washing step is carried out between the washing steps, wherebythe washing step can always be conducted with the cleaned elasticpolishing member, so that the lens mold can be washed without leavingdirt on the lens mold and without marring the lens mold.

In order to attain the first object mentioned above, according to thepresent invention, there is provided a scrubbing apparatus including: amold holding unit for holding and rotating a lens mold for molding aplastic lens; a pressing unit spaced from the mold holding unit; apolishing member holding unit for holding and rotating an elasticpolishing member; an operating unit for operating the mold holding unitand/or the polishing member holding unit so as to perform a washingoperation and a self-washing operation, the washing operation includingmoving the elastic polishing member or the lens mold while pressing theelastic polishing member against the lens mold, and the self-washingoperation including pressing the elastic polishing member against thepressing unit; and a liquid supplying unit for supplying a liquid to theelastic polishing member while the elastic polishing member isperforming the washing operation and the self-washing operation.

While the lens mold is held and rotated by the mold holding unit, theelastic polishing member is held and rotated by the polishing memberholding unit, the liquid is supplied from the liquid supplying unit,and, in this condition, the elastic polishing member is moved whilebeing pressed against the surface of the lens mold by the operatingunit, whereby the washing step is conducted. In addition, while theliquid is supplied from the liquid supplying unit, the elastic polishingmember being rotated by the polishing member holding unit is pressedagainst the pressing unit by the operating unit, whereby theself-washing step is conducted.

Preferably, the operating unit effects the washing operation and theself-washing operation alternately, and effects the self-washingoperation when the washing operation is at rest for a predeterminedperiod of time. When the washing operation is at rest for a long time,the elastic polishing member may be dried. With the self-washingoperation conducted when the washing operation is at rest for apredetermined period of time, it is possible to prevent the elasticpolishing member from being dried, and to prevent the lens mold frombeing marred.

Preferably, the liquid supplying unit supplied a slurry containing anabrasive dispersed in water. Where the slurry containing an abrasivedispersed in water is supplied to the surface of the lens mold, it ispossible to polishing the lens mold surface through the abrasive, and toeffectively remove dirt from the lens mold surface.

Preferably, the liquid supplying unit supplies water. In this case, itis possible to clean the surface of the lens mold through scrubbing withwater, to wash the elastic polishing member with water, and to removedirt or foreign matter deposited on the elastic polishing member itself.

In order to attain the second object mentioned above, according to thepresent invention, there is provided a lens mold drying methodincluding: a hot water supplying step of supplying water heated to apredetermined temperature to a surface of a lens mold for molding aplastic lens while rotating the lens mold; and a drying step ofsupplying dry air to the surface of the lens mold while rotating thelens mold, after the hot water supplying step.

With heated water poured to the lens mold being rotated, it is possibleto wash away the dirt or foreign matter present on the surface of thelens mold and to heat the lens mold. With dry air supplied whilerotating the lens mold, a uniform thin film of water is formed on thesurface of the lens mold, and thereafter the water on the surface isevaporated by the heat accumulated in the lens mold or by the heat ofthe hot water itself, so that the surface of the lens mold can be driedwithout leaving such defects as water discoloration and stains on thesurface. Therefore, good appearance quality can be obtained withoutusing an organic solvent and without needing a large-scale equipment forvacuum drying or the like.

Preferably, the heated water is pure water. With pure water used, it ispossible to dry the lens mold without leaving such defects as waterdiscoloration and stains on the surface of the lens mold.

In order to attain the second object mentioned above, according to thepresent invention, there is provided a lens mold drying apparatusincluding: a mold holding unit for holding and rotating a lens mold formolding a plastic lens; a hot water supplying unit for supplying waterheated to a predetermined temperature to a surface of the lens mold; anda dry air supplying unit for supplying dry air to the surface of thelens mold.

With heated water supplied from the hot water supplying unit to the lensmold being held and rotated by the mold holding unit, it is possible towash away the dirt or foreign matter from the surface of the lens mold,and to heat the lens mold. In addition, with dry air supplied from thedry air supplying unit to the lens mold being held and rotated by themold holding unit, it is possible to dry the lens mold. A uniform thinfilm of water is formed on the surface of the lens mold in the hot watersupplying step, and thereafter the water present on the surface isevaporated by the heat accumulated in the lens mold or by the heat ofthe hot water itself in the drying step, so that it is possible to drythe lens mold without leaving such defects as water discoloration andstains on the surface of the lens mold.

Preferably, the dry air supplying unit is disposed on the upper side ofthe mold holding unit, and a cover member surrounding the mold holdingunit is provided with an exhaust port in a lower portion thereof. Thedry air is supplied in the form of a downward flow, whereby waterpresent on the top face of the lens mold held by the mold holding unitcan be dried speedily.

In order to attain the third object mentioned above, according to thepresent invention, there is provided a method of manufacturing a plasticlens, including the steps of disposing a pair of lens molds opposite toeach other with a predetermined spacing therebetween, sealing the gapbetween the lens molds to form a lens-shaped cavity, charging a curablecomposition into the cavity, and curing the curable composition tothereby mold the plastic lens, wherein the curable composition is heatedto a temperature higher than room temperature or cooled to a temperaturelower than room temperature, and the temperatures of the pair of lensmolds are set to within ±10° C. from the temperature of the curablecomposition by heating or cooling.

Where the temperature difference between the lens molds and the curablecomposition is large, a convection would be generated in the chargedcurable composition, and, if the curable composition is cured in thepresence of the convection, internal strains would be generated, therebyspoiling the optical characteristics of the lens to be obtained. Evenwhere the curable composition being heated is injected into a lens moldassembly for cast polymerization of a plastic lens, setting a smalltemperature difference between the lens molds and the curablecomposition makes it possible to restrain the generation of a convectionin the curable composition, to restrain the generation of strains in thelens molded, and to enhance the yield of the lens.

Preferably, the pair of lens molds are heated by washing the lens moldsand/or by drying the lens molds with water heated to a predeterminedtemperature. With the lens molds heated in the washing step and thedrying step, the need for a separate heating equipment is eliminated,whereby it is possible to simplify the apparatus and to reduce cost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart of the process for cast polymerization molding ofa plastic lens;

FIG. 2(a) is a side view of female and male lens molds, and FIG. 2(b) isa perspective view of a lens mold assembly constructed by using thefemale and male molds and a pressure sensitive adhesive tape;

FIG. 3 is a conceptual diagram for illustrating the step of injecting acurable composition into the lens mold assembly;

FIG. 4 are plan views showing generally a lens mold washing apparatus,in which FIG. 4(a) shows the condition where lens molds are beingconveyed by a conveyor, and FIG. 4(b) shows the condition where the lensmolds are being washed;

FIG. 5 schematically show the structure of a gripping unit in theconveyor, in which FIG. 5(a) shows the condition immediately before thelens mold is gripped by the gripping unit, while FIG. 5(b) shows thecondition where the lens mold is gripped by the gripping unit, and ineach of FIGS. 5(a) and 5(b), the upper part is a side view and the lowerpart is a plan view;

FIG. 6 schematically shows the structure of a scrubbing apparatus;

FIG. 7 schematically shows the structure of a self-washing apparatus;

FIG. 8 schematically shows the structure of a drying apparatus; and

FIG. 9 schematically shows the structure of another drying apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, some embodiments of the present invention will be described below.It is noted, however, that the present invention is not limited to thefollowing embodiments.

The process for molding a plastic lens by cast polymerization, as shownin the flowchart in FIG. 1, comprises: a washing step of preparing afemale mold 1 having a convex surface molding surface 11 for a lens anda male mold 2 having a concave surface molding surface 21 for the lensand washing at least the molding surfaces of the molds; a water washingstep of washing the lens molds with water to remove an abrasive and thelike; a drying step of drying the lens molds having been wetted withwater; a mold assembly step of assembling the female mold 1 and the malemold 2 having been cleaned through the series of washing steps by a tapemold process or the like as shown in FIG. 2; a curable compositioninjection step of charging a curable composition into a cavity 4 of theconstructed lens mold assembly 5; a polymerization step of polymerizingand curing the charged curable composition 6; and a demolding step offinally obtaining the cured plastic lens out of the lens molds 1, 2.Where the molded plastic lens is a spectacle lens, the plastic lens isthen subjected selectively to polishing, dyeing, hard coat formation,antireflection film formation and the like, whereby a final plasticspectacle lens to be delivered to the wearer is obtained.

The scrubbing method and the scrubbing apparatus of the presentinvention for attaining the above-mentioned first object are used in thewashing step and the water washing step in the above molding process.

FIG. 4 show plan views of a lens mold washing apparatus in which systemseach comprising two scrubbing apparatuses and a lens mold dryingapparatus are arranged in parallel, whereby a female mold and a malemold can be subjected to a scrubbing step, a water washing step and adrying step in parallel and continuously. FIG. 4(a) shows the conditionwhere the lens molds are being conveyed by conveying units, and FIG.4(b) shows the condition where the lens molds are being washed.

The lens mold washing apparatus 100 has a structure in which a firstscrubbing apparatus 201, a first water scrubbing apparatus 301 and afirst drying apparatus 401 are arranged in one line in a clean area 101,and, opposite to this line, a second scrubbing apparatus 202, a secondwater scrubbing apparatus 302 and a second drying apparatus 402 arearranged in one line in the clean area 101. The units are surrounded bybottomed hollow cylindrical cover members 203, 303, 403. A conveyor 500for conveying the lens molds 1, 2 into and out of these units isdisposed. The conveyor 500 comprises an elongate main arm 501 extendinglong through a central area from the entrance side on the left towardthe exit side on the right, and the main arm 501 is reciprocated over apredetermined distance to the entrance side and the exit side. Centralportions of four transverse arms 511, 512, 513, 514 orthogonal to themain arm 501 are vertically movably mounted to the main arm 501 incorrespondence with the above-mentioned units, respectively, and a totalof eight gripping units 520 having the same structure for clamping andsupporting the lens molds 1, 2 are provided respectively at both ends ofthe transverse arms 511, 512, 513, 514. The gripping units 520 aresynchronously moved attendant on the reciprocating motions of the mainarm 501.

FIG. 5 schematically show the structure of the gripping unit 520. Thegripping unit 520 has a structure in which a pair of clamping arms 522driven toward and away from each other are supported on a support arm521 on one side thereof, and two each of cylindrical finger portions 522extending vertically downwards from each clamping arm 522 are provided.When the clamping arms 522 are moved toward each other, the side surfaceof the lens mold 1, 2 is supported at four locations by the fingerportions 523, and, when the clamping arms 522 are moved away from eachother, the finger portions 523 release the lens mold 1, 2.

As shown in FIG. 4, the conveyor 500 conveys the lens molds 1, 2 fromstand-by positions on the entrance side, in the manner of conveying, forexample, the male mold 2 sequentially into and out of the firstscrubbing apparatus 201, the first water scrubbing apparatus 301 and thefirst drying apparatus 401, while simultaneously conveying, for example,the female mold 1 sequentially into and out of the second scrubbingapparatus 202, the second water scrubbing apparatus 302 and the seconddrying apparatus 402. When the scrubbing apparatuses are operating, asshown in FIG. 4(b), the main arm 501 of the conveyor 500 is so disposedthat the transverse arms 511, 512, 513, 514 are disposed in the areasbetween the units. The female mold 1 and the male mold 2 arerespectively cleaned by being subjected sequentially to the scrubbingstep, the water washing step, and the drying step in parallel by theseunits, and are then simultaneously conveyed to a mold assembly unit (notshown).

The first scrubbing apparatus 201, the first water scrubbing apparatus301, the second scrubbing apparatus 202 and the second water scrubbingapparatus 302 are the same in basic structure. In the following, thecase of washing the male mold 2 will be described, the same beingapplied to the female mold 1 also.

FIG. 6 schematically shows the structure of the first scrubbingapparatus 201 as a representative of the scrubbing and water scrubbingapparatuses. A mold holding unit 210 for holding and rotating the malemold 2 is disposed substantially at the center of the inside of thehollow cylindrical cover member 203 (see FIG. 4). The mold holding unit210 comprises a rotary shaft 211, and a suction chuck 212 provided atthe upper end of the rotary shaft 211. The rotary shaft 211 is hollow,and is driven to rotate with a vertical axis as a center by a drivingmotor (not shown). The suction chuck 212 is for holding the male mold 2by suction, and is communicated with the hollow portion of the rotaryshaft 211. The conveyor 500 conveys in the male mold 2 in such a mannerthat the geometrical center of the circular male mold 2 coincides withthe center of the rotary shaft 211 and the lower surface of the malemold 2 makes contact with the suction chuck 212. A vacuum piping (notshown) is connected to the hollow portion of the rotary shaft 211, and,when the lower surface of the male mold 2 has come into contact with thesuction chuck 212, the suction chuck 212 is evacuated, whereby the lowersurface of the mole mold 2 can be held under suction by the suctionchuck 212. The upper surface of the male mold 2 thus held is a concavesurface molding surface 21 which needs precise cleaning. In the case ofthe female mold 1, a convex surface molding surface 11 is the uppersurface, and the lower surface is held by suction. In addition, insidethe cover member 203, a pressing unit 220 (see FIG. 4) in a rod-likeshape, for example, is disposed at a position away from the mold holdingunit 210 and close to the cover member 203. The pressing unit 220 willbe described later.

A short-axis cylindrical elastic polishing member 230 is rotatably heldon a polishing member holding unit 240 so that the circumferentialsurface of the elastic polishing member 230 can be rotated with ahorizontal axis as a center. The polishing member holding unit 240comprises a vertically standing support column 241, which is disposed onthe outside of the cover member 203. The support column 241 is driven torotate both clockwise and counterclockwise by a drive force suppliedfrom an operating unit 250, and can be moved upwards and downwardswithin a predetermined range. A base portion of a cantilever-typesupport arm 242 extending in a horizontal direction is attached to theupper end of the support column 241. A horizontal bearing 243 is fixedto the tip end of the support arm 242. One end portion of a flex shaft244 is supported on the bearing 243, and an end portion of the flexshaft 244 passed through the bearing 243 is fixed to a hollow portion atthe center of the elastic polishing member 230. The other end portion ofthe flex shaft 244 is connected directly to the rotary shaft of a motor245. The rotation of the motor 245 is transmitted to the elasticpolishing member 230 through the flex shaft 244. Therefore, the elasticpolishing member 230 is rotatably held on the polishing member holdingunit 240 so that it can be driven to rotate about a horizontalrotational axis. In addition, the elastic polishing member 230 can beswiveled attendant on the rotation of the support column 241 under thedriving of the operating unit 250, and can be moved upwards anddownwards attendant on the upward and downward movements of the supportcolumn 241.

The control of the rotation and vertical movements of the support column241 under the driving of the operating unit 250 is performed bysequential control, for example. The operating unit 250 effects: awashing operation in which the elastic polishing member 230 disposed onthe upper side of a substantially central portion of the male mold 2held and rotated by the mold holding unit 210 is moved downwards so thatthe elastic polishing member 230 being rotated is pressed against themale mold 2 being rotated and is thereby deformed, and the elasticpolishing member 230 being rotated is moved from the center to an endedge of the male mold 2 at a predetermined velocity; an operation inwhich the elastic polishing member 230 reaching the end edge of the malemold 2 is moved upwards to be spaced away from the male mold 2; aself-washing operation in which the elastic polishing member 230 locatedon the upper side of the end edge of the male mold 2 is moved in ahorizontal direction and is pressed against the pressing unit 220; andan operation in which, after the washed male mold 2 is conveyed from themold holding unit 210 to the next step by the conveyor 500, a new mold 2is held by the mold holding unit 210 and then the elastic polishingmember 230 being pressed against the pressing unit 220 is disposed onthe upper side of the center of the male mold 2. These operations arerepeated.

As the elastic polishing member 230, a liquid-permeable polishing spongecan be used. The material of the sponge is PVA, urethane, PP or thelike. In addition, at the time of forming the sponge, a sponge of PVA,urethane, PP or the like with an abrasive dispersed therein can be used.The elastic polishing member 230 with an abrasive dispersed therein canbe used both for the scrubbing apparatuses 201, 202 and for the washscrubbing apparatuses 301, 302. PVA is hard in its dried state and issoftened to be spongy when wetted. The shape of the elastic polishingmember 230 is generally a short-axis cylindrical shape, and may bedome-like, for example; namely, the shape is not particularly limited.The circumferential surface of the elastic polishing member 230 used forpolishing the lens molds 1, 2 may be rugged or may be smooth.

On the upper side of the elastic polishing member 230, a liquiddischarge port 260 is provided in the state of being fixed to thehorizontal arm 242 of the polishing member holding unit 240, whereby aliquid can be discharged from the upper side of the elastic polishingmember 230 to be supplied to the elastic polishing member 230. Theliquid discharge port 260 is so arranged that the liquid can always besupplied to the elastic polishing member 230 even when the elasticpolishing member 230 is moved. Since the elastic polishing member 230 iscomposed of a liquid-permeable sponge, the liquid supplied to theelastic polishing member 230 permeates through the elastic polishingmember 230, to be supplied to the surface of the male mold 2. When theelastic polishing member 230 is being pressed against the concavesurface molding surface 21 of the male mold 2, the liquid penetratesthrough the elastic polishing member 230, to be supplied to the areabetween the elastic polishing member 230 and the concave surface moldingsurface 21 of the male mold 2.

During the operation in which the elastic polishing member 230 ispressed against the male mold 2 and is moved from the center to the endedge of the male mold 2, the washing step is performed; during theoperation in which the elastic polishing member 230 is pressed againstthe pressing unit 220, the self-washing step is performed. During theseoperations of the elastic polishing member 230, the elastic polishingmember 230 is always rotated. At the time of washing the lens molds 1, 2in a continuous manner, the washing step and the self-washing step arealternately performed. Besides, when the male mold 2 is not fed induring the operation, the rotation of the elastic polishing member 230is stopped in the condition where the elastic polishing member 230 ispressed against the pressing unit 220, and the supply of the liquid isalso stopped; however, the rotation of the elastic polishing member 230and the supply of the liquid are conducted periodically, whereby theself-washing step is performed periodically.

FIG. 7 illustrates the concept of the condition where the self-washingstep is being performed. The circumferential surface of the elasticpolishing member 230 being rotated is pressed against the round rod-likepressing unit 220 and is thereby deformed. While the elastic polishingmember 230 is being thus deformed, the liquid L is supplied from theliquid discharge port 260 to the upper surface of the elastic polishingmember 230. In the first scrubbing apparatus 201 and the secondscrubbing apparatus 202, the liquid is water where the elastic polishingmember 230 is of the type of containing an abrasive dispersed therein,and the liquid is a slurry containing an abrasive dispersed in waterwhere the elastic polishing member 230 is of the type of not containingan abrasive. In the first water scrubbing apparatus 301 and the secondwater scrubbing apparatus 302, the liquid is water or water heated to apredetermined temperature, for the purpose of rinsing. As the water forrinsing, pure water is preferably used. As the abrasive, any of thoseabrasives which are commercially available generally for polishingglasses or metals can be used. Examples of the usable abrasives includemetal oxides such as Al₂O₃, CeO₂, SiO₂, SiO, ZrO₂, Cr₂O₃, etc., andcarbides such as SiC, C, etc. For the glass-made lens molds 1, 2, CeO₂can be used favorably. The grain size and shape of the abrasive arearbitrarily determined according to the material and shape of the lensmolds to be polished, the matter deposited on the surfaces of the lensmolds, or the desired surface roughness. The slurry containing anabrasive dispersed in water is used for the purpose of diffusing thefrictional heat between the elastic polishing member 230 and the lensmolds 1, 2, and for the purpose of enhancing the performance offollowing up to the shapes of the convex surface molding surface 11 andthe concave surface molding surface 21.

Thus, the self-washing step is a step of washing the elastic polishingmember 230 itself and removing the dirt therefrom, by supplying theliquid while deforming the elastic polishing member 230. With theself-washing step thus provided, it is possible to remove the dirt orforeign matter adhering to the elastic polishing member 230, to preventthe dirt or foreign matter from re-adhering to the lens molds 1, 2 fromthe elastic polishing member 230, and to achieve precise cleaning of thelens molds 1, 2. Particularly, in the method of constructing the lensmold assembly 5 by use of the pressure sensitive adhesive tape 3according to the tape mold process, the pressure sensitive adhesive ofthe pressure sensitive adhesive tape 3 may be left on the lens molds 1,2, and the residue of the pressure sensitive adhesive thus left mayadhere to the elastic polishing member 230, so that the residue of thepressure sensitive adhesive re-adheres to the lens molds 1, 2, causingcontamination. The self-washing step is effective for removing theresidue of the pressure sensitive adhesive. In addition, where washingis at rest for a long period of time, the elastic polishing member 230is dried, and, if washing is conducted by use of the elastic polishingmember 230 being in the dried state, the molding surfaces of the lensmolds 1, 2 would be marred. Therefore, the self-washing step also hasthe function of preventing the elastic polishing member 230 from beingdried, and the function of preventing the lens molds 1, 2 from beingmarred. Where the feeding-in of the lens molds 1, 2 is at rest for notless than a predetermined period of time during the operation, thedrying of the elastic polishing member 230 can be securely prevented byforcibly performing the self-washing periodically.

As a method for deforming the elastic polishing member 230 in theself-washing step, there is generally adopted a method in which a roundrod-like or hollow cylindrical pressing unit 220 and the elasticpolishing member 230 are pressed against each other. As for the size ofthe pressing unit 220, such a size is necessary that the pressing unit220 makes contact with the whole area of the circumferential surface,used for washing, of the elastic polishing member 230 when the elasticpolishing member 230 is rotated. The sectional shape of the pressingunit 220 may be round or polygonal; where the elastic polishing member230 is susceptible to marring in view of the material thereof, thesectional shape of the pressing unit 220 is desirably round. Examples ofthe material of the pressing unit 220 include iron, stainless steel,plastics, and ceramics. The effect of washing is lowered if the materialof the pressing unit 220 is too soft to endure the pressing of theelastic polishing member 230 thereagainst. Besides, such a material asto cause back contamination of the elastic polishing member 230 due torust or bleed-out cannot be used as the material of the pressing unit220. The pressing unit 220 is preferably so arranged that its portionbrought into contact with the elastic polishing member 230, at aposition where the elastic polishing member 230 is spaced away from thelens molds 1, 2 when the polishing member holding unit 240 is swiveled,is parallel to the rotational axis of the elastic polishing member 230and is brought into uniform contact with the circumferential surface ofthe elastic polishing member 230.

The scrubbing step performed by the first scrubbing apparatus 201 willbe described. The scrubbing step is applied also to the case where thefemale mold 1 is washed by the second scrubbing apparatus 202. The malemold 2 located in the stand-by position is conveyed into the firstscrubbing apparatus 201 by the conveyor 500, and the lower surface ofthe male mold 2 with the convex surface molding surface 21 up is held bythe suction chuck 212 of the mold holding unit 210 by suction. The moldholding unit 210 rotates the male mold 2 at a rate of 500 to 1000 rpm.While the polishing member holding unit 240 is rotating the elasticpolishing member 230 at a rate of 30 to 500 rpm, the operating unit 250rotates the support column 241 so as to dispose the elastic polishingmember 230 on the upper side of the male mold 2, and then lowers theelastic polishing member 230 to press the elastic polishing member 230against a central portion of the male mold 2. A slurry containing anabrasive is supplied from the liquid discharge port 260 to thecircumferential surface on the upper side of the elastic polishingmember 230. The quantity of the slurry supplied is appropriatelydetermined. If the quantity is too small, the dirt on the male mold 2cannot be removed sufficiently, and if the quantity is too large, theslurry may be spattered to the outside of the cover member 203 due tothe rotation of the lens molds 1, 2 and the elastic polishing member230. Where sufficient scrubbing can be achieved with the quantity of theslurry supplied at the time of self-washing, the slurry may notnecessarily be supplied during the scrubbing. While the elasticpolishing member 230 is pressed against the male mold 2 and rotated, itis moved from the center to the end edge of the male mold 2 to therebypolish the convex surface molding surface 21 through the abrasive. Inthe washing step, while the male mold 2 is rotated and theabrasive-containing slurry is supplied to the area between the elasticpolishing member 230 and the surface of the male mold 2, the elasticpolishing member 230 is rotated and pressed against the male mold 2 soas to movingly wash the male mold 2. By this washing step, the dirt orforeign matter present on the whole part of the concave surface moldingsurface 21 of the male mold 2 can be removed through rubbing with theabrasive.

After the washing step, the operating unit 250 rotates the supportcolumn 241 to move the elastic polishing member 230 from the lens mold 2to the pressing unit 220, and the self-washing step is conducted inwhich, while the elastic polishing member 230 is pressed against thepressing unit 220, the polishing member holding unit 240 rotates theelastic polishing member 230 at a rate of 30 to 500 rpm, and, in thiscondition, the liquid supplying unit 260 supplies theabrasive-containing slurry to the elastic polishing member 230, and theelastic polishing member 230 is deformed by the pressing member 220. Theperiod of time for which the self-washing is conducted varies dependingon the contamination condition of the elastic polishing member 230.However, it is desirable to set the period to such an extent as not toaffect the tact time of the washing; ordinarily, the period may beseveral seconds within the time for conveying the lens molds 1, 2. Inaddition, before the start of the washing and after a long-time rest ofthe washing, it is preferable to perform self-washing to wet and softenthe elastic polishing member 230, since the elastic polishing member 230in a dried state may damage the lens molds 1, 2.

By alternately performing the washing step and the self-washing step inthe scrubbing step, it is ensured that the self-washing step isconducted between the washing steps. By this, the washing step can beperformed always with the elastic polishing member 230 in the cleanedstate, so that the lens molds 1, 2 can be washed without leaving thedirt thereon and without marring them.

Where the elastic polishing member 230 is of the type of containing anabrasive dispersed therein, by only replacing the slurry with water, thewashing step and the self-washing step can be performed under the sameconditions as above.

Next, the water washing step performed by the first water scrubbingapparatus 301 will be described. The water washing step applies also tothe case of washing the female mold 1 by the second water scrubbingapparatus 302. For example, the male mold 2 having been scrubbed by thefirst scrubbing apparatus 201 is conveyed from the first scrubbingapparatus 201 into the first water scrubbing apparatus 301 by theconveyor 500, and the lower surface of the male mold 2 with the concavesurface molding surface 21 up is held by the suction chuck 212 of themold holding unit 210 by suction. The mold holding unit 210 rotates themale mold 2 at a rate of 500 to 1000 rpm. While rotating the elasticpolishing member 230 at a rate of 30 to 500 rpm, the polishing memberholding unit 240 moves the elastic polishing member 230 to dispose it onthe upper side of the male mold 2, and then lowers the elastic polishingmember 230 to press it against a central portion of the male mold 2.Water or water heated to a predetermined temperature is supplied fromthe liquid supplying unit 260 to the circumferential surface on theupper side of the elastic polishing member 230. While being pressedagainst the male mold 2, the elastic polishing member 230 is moved fromthe center to the end edge of the male mold 2, whereby the whole part ofthe concave surface molding surface 21 of the male mold 2 is rubbed withthe elastic polishing member 230. The water washing step is conducted inwhich, while the lens molds 1, 2 are rotated and the elastic polishingmembers 230 are rotated and pressed against the lens molds 1, 2, wateris supplied to the areas between the surfaces of the lens molds 1, 2 andthe elastic polishing members 230, thereby washing the lens molds 1, 2with water. By the water washing step, the abrasive and the likeremaining on the molding surfaces 11 and 21 of the lens molds 1, 2 canbe rubbed away.

After the washing step, the self-washing step is conducted, the elasticpolishing member 230 is moved from the male mold 2 to the pressing unit220, and the self-washing step is conducted in which, while the elasticpolishing member 230 is pressed against the pressing unit 220 and isrotated at a rate of 30 to 500 rpm, water or water heated to apredetermined temperature is supplied to the elastic polishing member230. Besides, before the start of the washing and after a long-time restof the washing, it is preferable to perform the self-washing step to wetand soften the elastic polishing members 230, since the elasticpolishing members 230 in a dried state may damage the lens molds 1, 2.Where heated water is used as the liquid to be supplied, the lens molds1, 2 can be heated to a temperature higher than room temperature, andcan be set close to the temperature of a warmed curable compositionwhich will be described later.

Also in the water washing step, with the washing step and theself-washing step performed alternately, it is ensured that theself-washing step is conducted between the washing steps, whereby thewater washing step can be performed always with the elastic polishingmembers 230 in the cleaned state, so that the lens molds 1, 2 can bewashed without leaving the dirt thereon and without marring them.

While the washing and the self-washing of the lens molds 1, 2 areperformed by moving the elastic polishing members 230 in the abovedescription, there may be adopted a method in which the elasticpolishing members 230 are fixed, whereas the mold holding units 210holding the lens molds 1, 2 and the pressing units 220 are moved so asto press the pressing units 220 against the elastic polishing members230, whereby the washing of the lens molds and the self-washing can beperformed in the same manner as above.

In addition, while it has been described above that the liquid supplyingunit moves together with the elastic polishing member and supplies thesame liquid both in the washing step and in the self-washing step, theremay be adopted a system in which liquid supplying units are disposedrespectively at the position of the washing step and at the position ofthe self-washing step, and different liquids are supplied respectively.

Next, the lens mold drying method and the lens mold drying apparatus ofthe present invention for attaining the above-mentioned second objectwill be described. The lend mold drying method and the lens mold dryingapparatus are used in the drying step in the flowchart shown in FIG. 1.

FIG. 8 schematically shows the structure of a first drying apparatus 401used in the lens mold washing apparatus 100 shown in FIG. 4. The seconddrying apparatus 402 is the same with the first drying apparatus 401 instructure. In the drying apparatus 401 shown in FIG. 8, a mold holdingunit 210 for holding and rotating a lens mold is disposed in a bottomedhollow cylindrical cover member 403. While the case of drying a malemold 2 for molding a concave surface is shown in FIG. 8, the sameapplies to a female mold 1. The mold holding unit 210 comprises a hollowrotary shaft 211 having a vertical axis, and the rotary shaft 211 isdisposed penetrating through the bottom wall of the cover member 403. Asuction chuck 212 is provided at the upper end of the rotary shaft 211,and a lower end portion of the rotary shaft 201 is in conjunction with arotary motor 213 at a lower portion of the cover member 403. A dry airsupplying unit 410 for blowing off dry air downwards is disposed on theupper side of the cover member 403. In addition, a nozzle-form hot watersupplying unit 420 for dripping hot water is disposed on the upper sideof the male mold 2 fixed to the suction chuck 212. The bottom surface ofthe lower portion of the cover member 403 is provided with an exhaustport 431. A truncated conical partition plate 432 for liquid dropseparation which is spaced from the rotary shaft 211 is provided insidethe cover member 403, whereby liquid drops falling from the male mold 2are discharged through a drain port 433. Dry air supplied from the dryair supplying unit 410 flows as a downward flow to pass through the gapbetween the rotary shaft 211 and the partition plate 432, and isdischarged through the exhaust port 431.

Besides, a drying apparatus as shown in FIG. 9 can also be used. Thedrying apparatus 401 b shown in FIG. 9 is the same as that shown in FIG.8 in basic structure. In this case, however, a side surface of a lowerportion of a cover member 403 b is provided with an exhaust port 431,and dry air supplied from a dry air supplying unit 410 flows as adownward flow to pass along the surface of a concave surface moldingsurface 21 of a male mold 2, and is discharged through the exhaust port431. In addition, the bottom surface of the cover member 403 b isinclined toward a drain port 433, so that liquid drops falling from themale mold 2 are drained through the drain port 433. The other structuresare the same as in FIG. 8, and, therefore, they are denoted by the samesymbols as used above and description thereof is omitted.

In the drying step in which these drying apparatuses 401, 401 b areused, the male mold 2 wetted by being washed with water by the firstwater scrubbing apparatus 301 is conveyed from the first water scrubbingapparatus 301 into the first drying apparatus 401 by the conveyor 500,and the lower surface of the male mold 2 is held onto the suction chuck212 by suction. While the mold holding unit 210 is rotating the malemold 2 at a predetermined rotation speed, a hot water supplying step isconducted in which hot water is dripped from a hot water supplying unit420 onto the surface of the concave surface molding surface 21 of themale mold 2. The hot water dripped is spread under a centrifugal force,to form a uniform thin film on the concave surface molding surface 21 ofthe male mold 2. Next, a drying step is conducted in which, while themold holding unit 410 is rotating the male mold 2 at a high speed toswish water off, dry air is supplied from the dry air supplying unit 410to the surface of the male mold 2, whereby the hot water film on thesurface of the concave surface molding surface 21 of the male mod 2 isevaporated, thereby drying the male mold 2.

In the hot water supplying step, not water at normal temperature but hotwater is used, for easier evaporation of water on the surfaces of thelens molds 1, 2, and for preventing the temperature from being lowereddue to the latent heat of evaporation. During when hot water issupplied, the rotating speed of the lens mold is preferably 50 to 300rpm, more preferably 100 to 200 rpm, the temperature of water ispreferably 30 to 100° C., more preferably 50 to 70° C., and the quantityof water discharged is preferably 2 to 200 ml, more preferably 10 to 100ml, where the surface area of the lens mold is 20 to 100 cm². Theseconditions can be determined taking into account the surface area,specific heat and thermal deformation temperature of the lens mold, thequality and quantity of dry air, the degree of replacement of theatmosphere, the temperature required of the mold in the subsequent step,etc. Another purpose of discharging water is to wash away the dirt suchas abrasive brought by the lens molds 1, 2 from the preceding step.Therefore, the quality of water supplied must be kept constant accordingto the clarity of the surface required in the steps after thewater-swishing and drying, and pure water is used, as required. Inaddition, the discharge of water is performed while rotating the lensmolds 1, 2, for the purpose of uniform washing. Water may notnecessarily be in the form of running water; for example, water may bein the form of spray, water vapor, or may be attended by ultrasonicwave.

The purpose of replacing the atmosphere on the surfaces of the lensmolds 1, 2 with dry air while rotating the molds at a high speed in thedrying step is to dry also the circumferential surfaces of the moldsafter drying the surfaces of the molds. In this case, for swishing wateroff, the rotating speed of the molds is preferably 200 to 3000 rpm, morepreferably 800 to 2000 rpm, the absolute humidity of dry air supplied ispreferably not more than 10 g/kg, more preferably not more than 5 g/kg,and the air quantity is preferably not less than 0.5 m³/min, morepreferably not less than 1.0 m³/min. For enhancing the atmospherereplacement efficiency, the exhaust port 431 is preferably provided onthe opposite side of the dry air supplying unit 410 with the male mold 2therebetween. With this arrangement, dry air blown off downwards fromthe dry air supplying unit 410 flows substantially vertically and flowsthrough the vicinity of the surface of the molding surface 21, to bedischarged through the exhaust port 431. Where the exhaust port is notprovided on the opposite side of the dry air supplying unit 410 with thelens molds 1, 2 therebetween, the humidity in the surroundings of thesurfaces of the lens mold 1, 2 would be raised, and drying would behindered. The surfaces of the lens molds 1, 2 are cooled by the latentheat of evaporation when dry air is supplied thereto. Therefore, wherethe exhaust port is not provided, re-dewing may occur on the surfaces ofthe molds after the surfaces are once dried, so that it may be necessaryto continue the supply of dry air until the atmosphere is replaced.Incidentally, dry air may be warmed.

Where there is no limitation as to the temperature required of the lensmolds in the subsequent step, it is possible to set the absolutehumidity of dry air at a high value and set the air quantity at a lowvalue, by setting a high hot-water temperature and setting a highdischarge quantity value. On the contrary, where the temperaturerequired of the lens molds in the subsequent step is near roomtemperature, it is necessary to set a low hot-water temperature and alow discharge quantity value, thereby setting the absolute humidity ofdry air at a low value and setting the air quantity at a high value.

As the dry air supplied, dry air obtained by use of a generaldehumidifier such as a cooling type dehumidifier using a refrigerant andan absorption type dehumidifier using silica gel or the like may beused, and compressed air may also be used, provided that a measure istaken to prevent liquid drops from being scattered at the time ofwater-swishing. Besides, dry air lowered in relative humidity by heatingair may also be used. The supply of dry air may be continued even at thetime of dripping hot water.

According to the lens mold drying method and drying apparatus asabove-described, by pouring warmed water to the lens mold being rotated,the dirt or foreign matter present on the surface of the lens mold canbe washed away. In addition, by supplying dry air while warming the lensmold and rotating the lens mold, it is ensured that a uniform thin filmof water is formed on the surface of the lens mold and thereafter thewater on the surface is evaporated by the heat accumulated in the lensmold or the heat of hot water itself, so that the lens mold can be driedwithout leaving such defects as water discoloration and stains on thesurface of the lens mold. Since an organic solvent such as a flon-based,alcohol-based or chlorine-based organic solvent or the like is not used,this system exerts little burden on the environments, and the apparatusmay not necessarily be provided with explosion-proof specifications.Besides, drying free of the troubles of water discoloration, stains andthe like can be achieved without adding a new step and while using asimple and inexpensive apparatus.

EXAMPLE 1

A plastic-molding glass molds with a diameter of 90 mm whose surfaceshad been scrubbed with a urethane-made sponge in the preceding step wasset in the drying apparatus 401 shown in FIG. 8.

While the glass mold was being rotated at a rate of 200 rpm, 20 ml ofpure water heated to 60° C. was discharged from the hot water supplyingunit 420 to a central portion of the surface of the glass mold.

Next, while the glass mold was being rotated at a rate of 2000 rpm, dryair with an absolute humidity of 5 g/kg was supplied from the dry airsupplying unit 410 at a rate of 1.0 m³/min. In this instance, dry airwas exhausted through the exhaust port 431 at a rate of 1.0 m³/min.

Thereafter, the glass mold was taken out, then the dried conditions ofthe surface of the glass mold and the side surface of a circumferentialportion of the glass mold were confirmed, and a plastic lens was moldedby use of the glass mold.

EXAMPLE 2

A plastic-molding glass mold with a diameter of 90 mm whose surface hadbeen immersed in an alkaline solution containing a surfactant in thepreceding step was set in the drying apparatus 401 b shown in FIG. 9.

While the plastic-molding glass mold with a diameter of 90 mm was beingrotated at a rate of 200 rpm, 30 ml of pure water heated to 70° C. wasdischarged from the hot water supplying unit 420 to a central portion ofthe surface of the plastic-molding glass mold.

Next, while the plastic-molding glass mold was being rotated at a rateof 2000 rpm, dry air with an absolute humidity of 3 g/kg was suppliedfrom the dry air supplying unit 410 at a rate of 2.0 m³/min. In thisinstance, dry air was exhausted through the exhaust port 431 at a rateof 2.0 m³/min.

Thereafter, the plastic-molding glass mold was taken out, and the driedconditions of the surface of the glass mold and the side surface of acircumferential portion of the glass mold were confirmed.

When the dried conditions of the surfaces and the circumferentialportion side surfaces of the glass molds subjected to water swishing anddrying in Examples 1 and 2 were checked, it was found that the surfacesand side surfaces of the glass molds had all been completely dried,without leaving water drops, fogs or the like thereon. In addition, whenplastic lenses were molded by use of the glass molds subjected to waterswishing and drying in Examples 1 and 2, the lenses obtained showed goodquality free of quality problems.

The female mold 1 and the male mold 2 cleaned by these washing steps areassembled into a lens mold assembly 5 shown in FIG. 2(b) by use of apressure sensitive adhesive tape in an assembling apparatus (not shown)connected to the lens mold washing apparatus 100.

In assembling the lens molds 1, 2, the centers of the lens molds 1, 2are determined, and, while the non-molding surface sides of the lensmolds 1, 2 are held, the center height of each molding surface relativeto a reference height is measured. Then, the lens molds 1, 2 are held insuch a manner that the centers of the lens molds 1, 2 are located on thesame line, and, in this condition, the lens molds 1, 2 are conveyed.Thereafter, arithmetic operation is performed based on the data of theheights of the center portions of the lens molds 1, 2 relative topredetermined reference positions, the lens molds 1, 2 are so held as toprovide a predetermined spacing between the molding surfaces of the lensmolds 1, 2, and, in this condition, the lens molds 1, 2 are conveyed.Finally, the pressure sensitive adhesive tape 3 is wound around thecircumferential surfaces of the lens molds 1, 2 over at least one turn,to form the lens mold assembly 5, and then the pressure sensitiveadhesive tape 3 is cut, to complete the process.

Besides, in assembling the lens molds 1, 2, a tubular resin-made gasketmay be used as a cavity-forming member. In this case, by press fittingthe lens molds 1, 2 into the gasket so as to provide a predeterminedspacing between the lens molds 1, 2, a lens mold assembly can be formed.

Next, the method of manufacturing a plastic lens according to thepresent invention for attaining the above-mentioned third object will bedescribed. In the curable composition injection step shown in FIG. 3,for enhancing injection efficiency, the viscosity of a curablecomposition 6 may be lowered to increase the injection flow rate througha small-diameter injection nozzle 7. A heater 11 may be disposed on theoutside surface of a pressure vessel 8, a heater 12 may also be woundaround a piping 9 constituting a conduit, and the heaters 11, 12 may beoperated to heat the curable composition 6 to a temperature higher thanroom temperature. For example, a photo-polymerization type curablecomposition less susceptible to be influenced by warming is warmed, tolower the viscosity of the curable composition. On the other hand, thereare curable compositions which are high in polymerization reactivityand, therefore, must be stored at a temperature lower than roomtemperature and be subjected to initial polymerization at a temperaturelower than room temperature. In the prior art, the temperature of thelens mold assembly 5 was room temperature, irrespectively of thetemperature of the curable composition.

However, if there is a large temperature difference between the lensmolds 1, 2 and the curable composition 6, a convection occurs in thecurable composition 6 charged. The convection does not disappear untilthe temperature difference becomes small. It has been found that whenthe curable composition 6 is cured in the presence of the convectiontherein, internal strains are generated, to spoil the opticalcharacteristics of the lens obtained, thereby causing a lowering in theyield of the product.

In view of the above, the curable composition 6 is heated to atemperature higher than room temperature or is cooled to a temperaturelower than room temperature, the temperature of the lens molds 1, 2 areset to within ±10° C. from the temperature of the curable composition 6,preferably to within ±5° C. from the temperature of the curablecomposition 6 by heating or cooling. By this, it was possible to enhanceconspicuously the yield of the plastic spectacle lens obtained uponmolding. From the viewpoint of energy saving, it is desirable to lowerthe temperature of the lens molds 1, 2 within the above-mentioned rangefrom the temperature of the curable composition.

The lens molds 1, 2 can be warmed or cooled, for example, by arranging ahot-air warmer or a heating furnace for warming the lens molds 1, 2 or athermostat for cooling the lens molds 1, 2, on the downstream side ofthe lens mold washing apparatus 100 shown in FIG. 4.

In the case of warming the lens molds 1, 2, water heated to apredetermined temperature may be used in the above-mentioned waterscrubbing apparatuses 301, 302 and the drying apparatuses 401, 402 usingthe heated water may be adopted, whereby the lens molds 1, 2 can bewarmed without using a special heating equipment. This system isadvantageous from the viewpoints of energy saving, equipment cost, andproduction lead time.

The temperature of water in the water scrubbing apparatuses 301, 302 isset at a temperature higher than the temperature of the curablecomposition 6 by at least 10° C., taking into account the time until theinjection of the curable composition 6 and the heat capacities of thelens molds 1, 2. The quantity of heated water to be used may be at sucha level that the lens molds 1, 2 can be sufficiently washed therewith.Depending on the thicknesses of the lens molds 1, 2, however, it may benecessary to supply heated water in an amount greater than that requiredfor washing. When the lens molds 1, 2 are warmed, there is the meritthat water present on the surfaces of the lens molds 1, 2 in thesubsequent drying step conducted by use of hot water is evaporatedquickly, whereby drying time can be shortened.

As for the heating of the lens molds 1, 2 by the drying apparatuses 401,402, when heated water is supplied in such a water quantity as to washaway the foreign matter, dirt and abrasive residue present on thesurfaces of the lens molds 1, 2, it is possible to sufficiently warm thelens molds 1, 2 by using the ordinary temperature and water quantity.Where heated water is not used in the water scrubbing apparatuses 301,302 or where the time until the injection of the curable composition 6is long, however, it may be necessary to supply water in a quantitygreater than the ordinary quantity.

Incidentally, when the viscosity of the curable composition 6 is high,the flow passage is disturbed at the time of injection to cause aphenomenon in which the curable composition 6 overflows in an unchargedcondition, in the cavity 4 in the lens mold assembly 5 for a lens withan extremely small thickness at the circumference thereof, such as aconvex lens. As a result, a failure due to uncharging occurs, making itnecessary to re-charge the curable composition, and causing an increasein the number of steps for readjustment. Thus, the warming of thecurable composition has the merit that the viscosity of the curablecomposition is lowered, the problems of uncharging is precluded, and theloss due to readjustment is precluded.

EXAMPLE 3

Water heated to the same temperature was supplied from hot pure watersupplying units to both the water scrubbing apparatuses 301, 302 and thedrying apparatuses 401, 402, whereby the lens molds 1, 2 were heated. Bysetting the set temperature of the hot pure water supplying units ateach of 60° C., 55° C., 50° C., 45° C., 40° C., 35° C., 30° C., and anunset value (normal temperature: 24° C.), the generation rate ofinternal strains relative to the temperature difference between thecleaned lens molds 1, 2 and the curable composition were investigated.The temperature of the curable composition at the time of charging wasset at 35° C., i.e., the temperature at which a failure due touncharging does not arise from disturbance of the flow passage at thetime of injection, even in the case of a lens with an extremely smallthickness at the circumference thereof, such as a convex lens. Theresults are shown in Table 1. TABLE 1 Temp. of Strain Set Temp. ofCurable Temperature Generation Temperature Mold Composition DifferenceRate 60° C. 48° C. 35° C. 13° C.  100%  55° C. 44° C. 35° C. 9° C. 2%50° C. 39° C. 35° C. 4° C. 0% 45° C. 35° C. 35° C. 0° C. 0% 40° C. 31°C. 35° C. 4° C. 0% 35° C. 28° C. 35° C. 7° C. 0.5%   30° C. 25° C. 35°C. 10° C.  8% Normal Temp. 24° C. 35° C. 11° C.  75%  24° C.

From the results given in Table 1, it is seen that the internal straingeneration rate can be reduced from 100% to 0%, by setting thetemperature difference between the lens molds and the curablecomposition to less than 10° C., preferably to less than 5° C.

In the above description, the convex surface molding surface of thefemale mold and the concave surface molding surface of the male moldhave been washed. In the case of using UV rays for curing the curablecomposition, however, it may be necessary to clean also the non-moldingsurfaces of the lens molds, for making perfect the light transmittanceof the lens molds.

INDUSTRIAL APPLICABILITY

The scrubbing method, the scrubbing apparatus, the lens mold dryingmethod, the lens mold drying apparatus, and the method of manufacturinga plastic lens according to the present invention pertains to atechnology for use in manufacturing a plastic lens such as a plasticspectacle lens by cast polymerization molding.

1. A scrubbing method comprising: a washing step of rotating a lens moldfor molding a plastic lens, pressing an elastic polishing member againsta surface of said lens mold while rotating said elastic polishingmember, and, in this condition, supplying a liquid to the area betweensaid surface of said lens mold and said elastic polishing member so asthereby to wash said lens mold; and a self-washing step of rotating saidelastic polishing member, supplying a liquid to said elastic polishingmember, and, in this condition, deforming said elastic polishing memberso as thereby to wash said elastic polishing member.
 2. A scrubbingmethod as set forth in claim 1, wherein said liquid used in said washingstep and said self-washing step is a slurry containing an abrasivedispersed in water.
 3. A scrubbing method as set forth in claim 1,wherein said liquid used in said washing step and said self-washing stepis water.
 4. A scrubbing method as set forth in claim 1, whereinself-washing is conducted while deforming said elastic polishing memberby pressing said elastic polishing member and a rod-like member againsteach other.
 5. A scrubbing method as set forth in claim 1, wherein saidwashing step and said self-washing step are conducted alternately.
 6. Ascrubbing apparatus comprising: a mold holding unit for holding androtating a lens mold for molding a plastic lens; a pressing unit spacedfrom said mold holding unit; a polishing member holding unit for holdingand rotating an elastic polishing member; an operating unit foroperating said mold holding unit and/or said polishing member holdingunit so as to perform a washing operation and a self-washing operation,said washing operation comprising moving said elastic polishing memberor said lens mold while pressing said elastic polishing member againstsaid lens mold, and said self-washing operation comprising pressing saidelastic polishing member against said pressing unit; and a liquidsupplying unit for supplying a liquid to said elastic polishing memberwhile said elastic polishing member is performing said washing operationand said self-washing operation.
 7. A scrubbing apparatus as set forthin claim 6, wherein said operating unit effects said washing operationand said self-washing operation alternately, and effects saidself-washing operation when said washing operation is at rest for apredetermined period of time.
 8. A scrubbing apparatus as set forth inclaim 6, wherein said liquid supplying unit supplies a slurry containingan abrasive dispersed in water.
 9. A scrubbing apparatus as set forth inclaim 6, wherein said liquid supplying unit supplies water.
 10. A lensmold drying method comprising: a hot water supplying step of supplyingwater heated to a predetermined temperature to a surface of a lens moldfor molding a plastic lens while rotating said lens mold; and a dryingstep of supplying dry air to said surface of said lens mold whilerotating said lens mold, after said hot water supplying step.
 11. A lensmold drying method as set forth in claim 10, wherein said heated wateris pure water.
 12. A lens mold drying apparatus comprising: a moldholding unit for holding and rotating a lens mold for molding a plasticlens; a hot water supplying unit for supplying water heated to apredetermined temperature to a surface of said lens mold; and a dry airsupplying unit for supplying dry air to said surface of said lens mold.13. A lens mold drying apparatus as set forth in claim 12, wherein saiddry air supplying unit is disposed on the upper side of said moldholding unit, and a cover member for surrounding said mold holding unitis provided with an exhaust port in a lower portion thereof.
 14. Amethod of manufacturing a plastic lens, comprising the steps ofdisposing a pair of lens molds opposite to each other with apredetermined spacing therebetween, sealing the gap between said lensmolds to form a lens-shaped cavity, charging a curable composition intosaid cavity, and curing said curable composition to thereby mold theplastic lens, wherein said curable composition is heated to atemperature higher than room temperature or cooled to a temperaturelower than room temperature, and the temperatures of said pair of lensmolds are set to within ±10° C. from the temperature of said curablecomposition by heating or cooling.
 15. A method of manufacturing aplastic lens as set forth in claim 14, wherein said pair of lens moldsare heated by washing said pair of lens mold and/or by drying said pairof lens molds with water heated to a predetermined temperature.